The present invention relates generally to a high-breakdown-voltage semiconductor apparatus and more particularly to a high-breakdown-voltage semiconductor apparatus having a plurality of IGBTs.
An IGBT (Insulated Gate Bipolar Transistor) is known as one of high-breakdown-voltage semiconductor devices used in a high-breakdown-voltage apparatus for performing power control. The IGBT is a modern device having both high-speed switching characteristics of a MOSFET and high-output characteristics of a bipolar transistor. IGBTs have recently been used in the wide field of power electronics, e.g. inverters, switching power supply, etc.
The IGBT, however, has the following problems.
In the IGBT, as compared to a high-breakdown-voltage semiconductor device such as a thyristor for latching-up, the amount of carriers injected from the source side is small and the turn on/off characteristics are degraded. In addition, since the thickness of the base layer increases as the breakdown voltage is higher (in particular, 3 kV or above), the turn on/off characteristics are more degraded.
In order to solve these problems, there is a technique to increase the width (gate width) of the gate electrode.
However, if the gate width is increased, the input capacitance or feedback capacitance of the MOS gate portion increases. Consequently, the switching speed lowers, the current or voltage varies at the time of switching, or malfunction occurs due to external noise. Such a decrease in switching speed or malfunction leads to unstable operations of the apparatus. In worst cases, the apparatus is destroyed.
In the conventional IGBT, as described above, the amount of carriers injected from the source side decreases and the turn on/off performance deteriorates as the breakdown voltage increases. If the gate width is increased in order to solve these problems, the switching speed lowers or malfunction occurs. Consequently, the operation of the apparatus becomes unstable.